SEARCH · Engineering Papers

Results for “particulate”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58

All sources NASA NTRS DOE OSTI

NASA NTRS1975

Criteria for identification of ablation debris from primitive meteoric bodies

Samples of ablated materials are analyzed to determine properties expected to be characteristic of particulates generated by the ablation of primitive meteoric bodies. Analyses of carbonaceous-chondrite fusion crusts and samples artificially ablated in the laboratory indicate that most meteor-ablation debris should consist of assemblages of silicate minerals, principally olivine, and micron-sized magnetic grains. It is expected that ablation debris of at least 10 microns should have abundances of Fe, Mg, Si, Ca, and Ni similar to those found in chondritic meteorites. Volatile species such as S, H2O, and Cl are lost during ablation and normally should not be found in ablated material. The major findings of this study are supported by analysis of spherules collected in the atmosphere which are thought, on separate grounds, to be genuine meteor-ablation products. The majority of meteoric bodies probably have cometary origins, and it is hoped that the ability to collect and identify meteor-ablation debris reliably will provide an opportunity to do laboratory analysis of cometary matter.-

Brownlee, D. E.↗

NASA NTRS1975

Composition of the Martian dust as derived by infrared spectroscopy from Mariner 9

The Martian dust spectra obtained by the infrared interferometer spectrometer (Iris) experiment on Mariner 9 have been compared with modeling computations for various minerals and rocks. The model used was based upon a recently developed theory of absorption and scattering by particulate materials. The results indicate that the composition of Martian dust is biased toward silicate structures which involve a high degree of silicate oxygen sharing. A feldspar-rich dust of approximately 1-micron particle size appears to be the best candidate, although sheet-structure silicates cannot be ruled out.

Aronson, J. R.↗

NASA NTRS1975

Integrated investigation of the mixed origin of lunar sample 72161,11

The comminution-agglutination model and the solar-wind implantation-retention model are used to postulate the origins of the particulate components of lunar sample (72161,11), a submillimeter fraction of a surface sample for the dark mantle regolith at LRV-3. Grain-size analysis was performed by wet sieving with liquid argon, and analyses for CO2, CO, CH4, and H2 were carried out by stepwise pyrolysis in a helium atmosphere. The results indicate that the present sample is from a mature regolith, but the agglutinate content is only 30% in the particle-size range between 90 and 177 microns, indicating an apparent departure from steady state. Analyses of the carbon, methane, and hydrogen concentrations in size fractions larger than 149 microns show that the volume-correlated component of these species increases with increased grain size. It is suggested that the observed increase can be explained in terms of mixing of a dominant local population of coarser agglutinates having high carbon and hydrogen concentrations with an imported population of finer agglutinates relatively poor in carbon and hydrogen.

Basu, A.↗

NASA NTRS1975

ATS-6 - Solar cell flight experiment after 325 days in synchronous orbit

Preliminary results of the Applications Technology Satellite-6 (ATS-6) solar cell flight experiment to isolate and identify solar cell degradation mechanisms resulting from particulate radiation and to obtain specific design data applicable to extended synchronous spacecraft missions are presented. The experiment includes 80 individual cells representing 16 different solar cell/cover glass configurations. Most of the cells are 0.030 cm thick boron doped n/p cells with 10 ohm cm resistivity and solder-coated AgTi contacts. The voltage-current characteristics were measured regularly. The data for the first 325 days of flight show short circuit currents 1-8% higher than measurements made with solar simulations. Maximum power varied between -1 and +6%. After 50 days in orbit the degradation of short circuit current due to ultraviolet effects was determined to be about 2%. All cells except those with fluorinated ethylene propylene covers performed well after 325 days.

Goldhammer, L. J.↗

NASA NTRS1976

Stratospheric aluminum oxide

Balloons and U-2 aircraft were used to collect micrometer-sized stratospheric aerosols. It was discovered that for the past 6 years at least, aluminum oxide spheres have been the major stratospheric particulate in the size range from 3 to 8 micrometers. The most probable source of the spheres is the exhaust from solid-fuel rockets.

Brownlee, D. E.↗

NASA NTRS1976

International Conference on Environmental Sensing and Assessment, Las Vegas, Nev., September 14-19, 1975, Proceedings. Volumes 1 & 2

The papers deal with the detection of hazardous environmental pollutants, the development of emission control plans, and the design of compliance monitoring systems. Topics include remote sensing techniques in environmental pollution monitoring, monitoring of atmospheric particulate matter, air pollution due to sulfur dioxide and other inorganic compounds, marine pollution, atmospheric aerosols, industrial pollution, and legal aspects of pollution monitoring. Other papers examine the toxic effects of heavy metals and halogenated hydrocarbons, pollution associated with waste-disposal processes, pesticide residues in soil and groundwater, evaluations of groundwater quality, and monitoring of nuclear wastes. The interaction of climate and pollution is also discussed along with global pollutant transport, environmental modeling, ambient environmental air quality, aircraft and ground-vehicle emissions, and pollution associated with energy extraction and utilization processes. Individual items are announced in this issue.

Source record↗

NASA NTRS1976

An automated atmospheric sampling system operating on 747 airliners

An air sampling system that automatically measures the temporal and spatial distribution of particulate and gaseous constituents of the atmosphere is collecting data on commercial air routes covering the world. Measurements are made in the upper troposphere and lower stratosphere (6 to 12 km) of constituents related to aircraft engine emissions and other pollutants. Aircraft operated by different airlines sample air at latitudes from the Arctic to Australia. This unique system includes specialized instrumentation, a special air inlet probe for sampling outside air, a computerized automatic control, and a data acquisition system. Air constituent and related flight data are tape recorded in flight for later computer processing on the ground.

Perkins, P. J.↗

NASA NTRS1976

Low pressure radon diffusion - A laboratory study and its implications for lunar venting

Results of a study of radon migration through columns of fine particulate materials, at total pressures of 0.02-0.2 torr, are reported. Materials studied were: NBS Glass Spheres (SRM 1003), Emerson & Cuming Eccospheres (IG-101), activated coconut charcoal, Lipaci obsidian, and W-1 Standard Diabase. Rates of diffusion were used to derive heats of adsorption for radon on the materials tested. The most reliable values found clustered around 8-9 kcal/mole. These high heats of adsorption, if typical for most materials, combined with low percentages of radon emanation by lunar soils found by other researchers, imply that random walk diffusion will not be an important mechanism for redistributing the radon and the radon daughters produced in the lunar regolith. In particular, since random walk migration is not a sufficient mechanism to account for localized high concentrations of radon-222 and its daughter polonium-210 observed by the Apollo 15 and 16 command modules, an alternative mechanism is proposed, in which radon would be swept to the surface by other gases during intermittent venting events.

Friesen, L. J.↗

NASA NTRS1976

Minor planets and related objects. XX - Polarimetric evidence for the albedos and compositions of 94 asteroids

Polarimetric observations are presented and analyzed for a total of 94 asteroids. The data include numerical parameters describing the polarization-plane curve, the maximum depth of the negative branch, geometric albedo, and diameter. With few exceptions, the polarizations are found to be repeatable from hour to hour, night to night, and apparition to apparition at the same solar phase angle within an observational accuracy of plus or minus 0.05%. It is shown that over a range of more than a factor of 50 in diameter or a factor of 100,000 in mass, all the asteroids seem to have microscopically very rough or particulate surface textures. In terms of their polarimetric properties, the asteroids are classified as follows: 48 in the broad S class, with compositions corresponding to stony-iron meteorites or ordinary chondrites; 34 in the C class, probably corresponding to carbonaceous chondrites; three to five M asteroids with surfaces rich in free metal; two with low-opacity surfaces (class E) attributable to pure enstatite; and five of other types.

Zellner, B.↗

NASA NTRS1976

Physical properties of asteroid 433 Eros

Newly available photometric, polarimetric, spectroscopic, thermal-radiometric, radar, and occultation results are synthesized in order to derive a coherent model for Eros. The geometric albedo is 0.19 plus or minus 0.01 at the visual wavelength, and the overall dimensions are approximately 13 by 15 by 36 km. The rotation is about the short axis, in the direct sense, with a sidereal period of 5 hr 16 min 13.4 sec. The pole of rotation lies within a few degrees of ecliptic coordinates 16 deg longitude and beta = +11 deg latitude. Eros is uniformly coated with a particulate surface layer several millimeters thick. It has an iron-bearing silicate composition, similar to that of a minority of main-belt asteroids, and probably identifiable with H-type ordinary chondrites.

Zellner, B.↗

NASA NTRS1976

Direct observation of small cluster mobility and ripening

Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single-crystalline thin graphite substrates have been studied by in situ transmission electron microscopy (TEM) under controlled environmental conditions in the temperature range from 25 to 450 C. It was possible to monitor all stages of the experiments by TEM observation of the same specimen area. Slow Ostwald ripening was found to occur over the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility. This was concluded from in situ observations of individual particles during annealing and from measurements of cluster size distributions, cluster number densities, area coverages, and mean cluster diameters.

Heinemann, K.↗

NASA NTRS1976

Optical and physical requirements for fluid particles marking trailing vortices from aircraft

A theoretical study of the optical and physical requirements of marking trailing vortices that emanate from aircraft wings was carried out by considering particulate light-scattering properties, ability of particles to follow trailing vortices, and survival time of particles to vortex dissipation. Liquid droplets undergoing evaporation and molecular dispersion were investigated. Droplets should have lifetimes of about 300 sec. Droplet size should be about 1 micron to maximize light scattering with the minimum mass of liquid required. Droplets of this small size would spiral outward very slowly and essentially remain in the vortex cores. Nontoxic hygroscopic liquids, having an affinity for moisture in the air, have been identified. These liquids have relatively low vapor pressures of order 10 to the -5 mm Hg that would insure droplet persistence long enough to mark trailing vortices.

Back, L. H.↗

NASA NTRS1975

Contamination control coatings for hybrids

Conductive particles unexpectedly present in hermetically sealed hybrid microcircuit packages pose a high risk of shorting the closely spaced planar conductors within the package, causing failure of the device. The present work evaluates commercially available organic coating materials and determines the most promising ones for protection of complex microcircuits against entrapped particulate contaminants. The candidate materials were exposed to a series of physical and electrical screening tests, the results of which were used as a basis for the final coating selection. Silicones and high-purity epoxies are found to not only display excellent compatibility with microcircuits but to improve the performance of microcircuits as to voltage breakdown between adjacent conductors.

Mastro, A. R.↗

NASA NTRS1976

Lidar observations of the stratospheric aerosol - California, October 1972 to March 1974

The paper describes the results of a series of 30 observations of stratospheric aerosol made with a ground-based lidar on the North Pacific Coast during a period relatively uninfluenced by major volcanic penetrations and displaying a relative temporal minimum in particulate content. The objectives were to provide a record of aerosol behavior during this intervolcanic period, to compare this behavior with that revealed by previous studies using a variety of techniques, and to provide comparative data on the stratospheric aerosol by conducting joint lidar and aircraft observations. Determination of scattering profile ratios from lidar signal profiles and analysis of experimental errors are described. Analysis of the data shows that significant temporal variability of the aerosol was observed, probably of nonvolcanic origin. Much of the variability was confined to the 23-30 km height region, above the major peak in scattering ratio. The evidence is that this is not due to influxes of extraterrestrial material. Vertical motions of the centroid of the scattering ratio peak were recorded during the 1973 stratospheric warming, and illustrate the value of lidar's ability to monitor temporal variations of vertical structure.

Russell, P. B.↗

NASA NTRS1975

Optical design of the SBUV/TOMS experiment on Nimbus G

The paper examines the tradeoffs performed in optimizing the optical design of the solar backscatter ultraviolet/total ozone mapping spectrometer (SBUV/TOMS) experiment on Nimbus G to stringent performance requirements within the limitations of the spacecraft interface. The SBUV portion of the experiment incorporates a double monochromator optimized for better than 1.0 A spectral resolution over the wavelength range 1600-4000 A. The TOMS portion of the experiment is a stepped line scanning system with a 105-deg total field of view. Special techniques are used to reduce the polarization sensitivity of the instrument to less than 5% for 100% linearly polarized incident radiation and to keep the spectral stray light to less than 0.000001 of the incident solar spectrum. Optical material selection is imperative in order to minimize the effects of fluorescence and phosphorescence arising from the bombardment of particulate radiation in space.

Henderson, B. D.↗

NASA NTRS1977

Dust-contamination monitor

Compact instrument gives instantaneous reading of accumulation of small particles on glass plate. Instrument is sensitive to particles as small as one hundred microns and should be adaptable to monitoring particulate air pollution or dust levels in semiconductor clean rooms. Dual collimated light sources produce highly monochromatic radiation direct at grazing single angle onto glass plate.

Claysmith, C. R.↗

NASA NTRS1976

Influence of acoustics in separation processes

The effects of introducing high energy acoustics into various filtering and drying systems were studied. With very slow velocity filtration systems, it was found that the introduction of acoustics could substantially increase the flow rate and also aided in the coagulation of the particulates before reaching the filter media. In the drying of temperature sensitive powders, the rate was increased by the introduction of acoustics. The acoustic frequency used was 20 kHz with power levels up to 3 watts per square centimeter.

Fairbanks, H. V.↗

NASA NTRS1976

Wind measurement system

A system for remotely measuring vertical and horizontal winds present in discrete volumes of air at selected locations above the ground is described. A laser beam is optically focused in range by a telescope, and the output beam is conically scanned at an angle about a vertical axis. The backscatter, or reflected light, from the ambient particulates in a volume of air, the focal volume, is detected for shifts in wavelength, and from these, horizontal and vertical wind components are computed.

Cliff, W. C.↗